Effects of Aluminum and Manganese on the Growth of Ectomycorrhizal Fungi

Cenococcum graniforme, Suillus luteus, Thelephora terrestris, and three isolates of Pisolithus tinctorius were cultured on modified Melin-Norkrans medium at pH 3.4 and adjusted to 0 to 500 ppm (0 to 500 μg/ml) of aluminum or manganese sulfate. Except for T. terrestris, which was intolerant of aluminum at 150 and 250 to 500 ppm, and P. tinctorius isolate 250, which was intolerant of aluminum at 450 ppm, all fungi showed some growth at all concentrations of aluminum. S. luteus was the most tolerant to aluminum. Manganese was less fungitoxic than aluminum, with all fungi showing at least 65% growth at 500 ppm as compared with the control. C. graniforme was not inhibited at any concentration of manganese, and S. luteus was only affected at 500 ppm. P. tinctorius isolate 230 showed no significant variation in growth when subjected to various concentrations of three forms of manganese salts. Significant differences in growth were detected in response to three aluminum salts, but no detectable pattern was apparent. Genotypic responses to aluminum and manganese were evident for P. tinctorius. Isolates 210 and 230 were more tolerant to manganese than was isolate 250. Aluminum tolerance was in the order of isolate 230 > 210 > 250. Results of in vitro studies concerning tolerance responses of ectomycorrhizal fungi to aluminum and manganese were not consistent with field observations of the successional sequence of these fungi on acid coal spoils.     

Aluminum Elicits Exocellular Phosphatidylethanolamine Production in Pseudomonas fluorescens

Pseudomonas fluorescens ATCC 13525 was found to grow in a minimal mineral medium supplemented with millimolar amounts of aluminum, a known environmental toxicant. During the stationary phase of growth, the trivalent metal was localized in a phosphatidylethanolamine (PE)-containing residue. The concentration of PE in pellets ranged from 1.7 to 13.9 mg ml of culture(sup-1) in media supplemented with 1 to 30 mM aluminum. Although the gelatinous residue was observed during the stationary phase of growth, ultracentrifugation and dialysis experiments revealed that PE was produced from earlier stages of incubation and was associated with aluminum. A sharp diminution in the levels of PE and aluminum in the spent fluid was concomitant with the formation of the insoluble deposit. The aluminum content of the soluble cellular fraction increased during growth and reached an optimum of 1.85 mM of test metal at 45 h in cultures with 15 mM aluminum. Further incubation, however, led to a marked decrease in the cellular aluminum content, and during the stationary phase of growth, only trace amounts of the trivalent metal were detected in this fraction. When 45-h cells were incubated in fresh citrate medium, most of the intracellular aluminum was secreted in the spent fluid and citrate was rapidly consumed. Aluminum efflux was also observed in cultures in which d-glucose was substituted for citrate. However, no efflux of this trivalent metal was evident in media devoid of either citrate or d-glucose. Scanning electron microscopic studies and X-ray energy-dispersive analyses of the dialyzed supernatant aided in the visualization of nodule-like aluminum- and phosphorus-rich bodies associated with thread-like carbon-, oxygen-, and phosphorus-containing structures. Transmission electron microscopic and electron energy loss spectroscopic analyses revealed the presence of aluminum within bacteria after 45 h of incubation. Cells harvested after aluminum insolubilization did not shown aluminum inclusions. This aluminum-tolerant microbe may have potential application in bioremediation processes.     

Aluminum and calcium distribution patterns in aluminum-intoxicated roots of Allium cepa do not support the calcium-displacement hypothesis and indicate signal-mediated inhibition of root growth

The aluminum and calcium distributions in the root tips of aluminum-intoxicated onions, Allium cepa L., were mapped using PIXE (particle-induced X-ray emission) microanalysis. Not enough aluminum was present to have replaced, atom-for-atom, more than a minor fraction of the calcium. Furthermore, no inverse relationship between variations in aluminum and calcium concentrations was observed for pairs of adjacent 30-μm-diameter regions. Our observations, therefore, do not support the hypothesis that aluminum substantially reduces the quantity of bound calcium by competing with calcium for binding sites. Instead we suggest that reductions in calcium content are a non-local and indirect consequence of aluminum-intoxication. We found that aluminum accumulates almost exclusively in a surface layer. Observations of wounded roots indicated that exposed internal tissue binds aluminum avidly, so we contend that the surface accumulation pattern indicates that little aluminum penetrates into the interior of the root. We argue that aluminum does not directly inhibit growth in the interior of the apical root meristem because root growth rate was unaffected by root cap removal which should greatly increase the aluminum concentration in the exposed interior region. We hypothesize that growth inhibition in the interior of the meristem is mediated by a signal initiated or disrupted by excess aluminum in the periphery of the meristem. Received: 29 January 1997 / Accepted: 10 June 1997     

Inducible aluminum resistance of Acidiphilium cryptum and aluminum tolerance of other acidophilic bacteria

Aluminum ions are highly soluble in acidic environments. Toxicity of aluminum ions for heterotrophic, facultatively and obligately chemolithoautotrophic acidophilic bacteria was examined. Acidiphilium cryptum grew in glucose-mineral medium, pH 3, containing 300 mM aluminum sulfate [Al(2)(SO(4))(3)] after a lag phase of about 120 h with a doubling time of 7.6 h, as compared to 5.2 h of growth without aluminum. Precultivation with 1 mM Al(2)(SO(4))(3) and transfer to a medium with 300 mM Al(2)(SO(4))(3) reduced the lag phase from 120 to 60 h, and immediate growth was observed when A. cryptum was precultivated with 50 mM Al(2)(SO(4))(3), suggesting an aluminum-induced resistance. Aluminum resistance was not induced by Fe(3+) ions and divalent cations. Upon exposure of A. cryptum to 300 mM Al(2)(SO(4))(3), the protein profile changed significantly as determined by SDS-PAGE. When other acidophiles were cultivated with 50-200 mM aluminum sulfate, no lag phase was observed while the growth rates and the cellular yields were significantly reduced. This growth response was observed with Acidobacterium capsulatum, Acidiphilium acidophilum, Acidithiobacillus ferrooxidans, and Acidithiobacillus thiooxidans. Precultivation of these strains with aluminum ions did not alter the growth response caused by aluminum. The content of A. cryptum cultivated with 300 mM Al(2)(SO(4))(3)was 0.44 microg Al/mg cell dry weight, while that of the other strains cultivated with 50 mM Al(2)(SO(4))(3) ranged from 0.30 to 3.47 microg Al/mg cell dry weight.     

小麦地上部和根系生长的相关性及其在耐Al性筛选中的作用

1　引　　言以往的研究中 ,测定植物根系长度或重量通常以相对根长或相对根系干重作为耐性指标进行耐Ａｌ性的筛选[2 ,4 ,5,8] .但是根系性状在土培或田间试验中不仅取样和测定困难 ,而且易造成根系损伤 ,影响测定的精度 .因此 ,有必要建立简便、可靠且易于测定的筛选指标 .能否采用植株地上部耐性指标来衡量不同小麦基因型的耐Ａｌ性 ?以往涉及植物在铝毒胁迫下地上部和根系生长的耐性指标间的相关性 ,以及地上部耐性指标用于耐Ａｌ性筛选方面的研究甚少 .本研究采用两种筛选方法探讨了 2 4个小麦基因型地上部和根系耐性指标间的相关性 ,旨…     

Aluminum transfer through milk in female rats intoxicated by aluminum chloride

Female rats received an ip injection of aluminum chloride, (10 mg Al/kg/d) during the first 12 d after parturition; this treatment led to a reduction in food intake associated with a reduction in body wt. Pups of the intoxicated dams showed a growth retardation after postnatal day 7. One day after treatment, the female rats intoxicated with aluminum had a considerably higher level of aluminum in milk than controls. The aluminum levels of plasma, liver, spleen, and kidneys were also significantly higher in treated female rats than controls. On the contrary, in the same tissues of pups from treated or not treated dams, no differences in aluminum levels were observed. No effect of aluminum treatment was detected on plasma silicon levels in dams and pups.     

Aluminum Uptake by Neuroblastoma Cells

Aluminum uptake studies in viable neuroblastoma cells were performed. Aluminum uptake was largely dependent on the pH of the suspension medium. At physiological pH values, cells were apparently unable to incorporate detectable amounts of aluminum in the absence of proper mediators. Aluminum uptake was enhanced as the pH decreased, attaining a plateau at about pH 6.0. In experiments with 2 x 10(6) cells/ml, pH 6.0, and 25 microM aluminum in the medium, aluminum incorporation reached saturation at 5 nmol of aluminum/mg of cellular protein, accounting for 60-70% of aluminum added. At pH 6.0, cells showed a large capacity for accumulating aluminum; about 70% of intracellular aluminum was associated with the postmitochondrial fraction. At neutral pH, application of apotransferrin seemed to facilitate aluminum translocation into cells via membrane receptors. Fatty acids were also capable of mediating aluminum uptake at neutral pH, probably by forming aluminum-fatty acid complexes. Low molecular weight aluminum chelators, e.g., citrate, inhibited aluminum uptake. Treatment of cells with energy metabolism blockers had virtually no influence on aluminum uptake, indicative of passive mechanisms. The results suggest that aluminum uptake occurs via different modes dependent on growth conditions, such as medium pH.     

粘盖乳牛肝菌在低磷、酸铝胁迫下的生长和代谢响应

低磷和酸铝胁迫是酸性土壤限制植物生长的主要因素。有研究指出外生菌根(ectomycorrhiza,ECM)可提高宿主植物对铝毒害和低磷胁迫的适应性。然而,目前有关ECM真菌自身对低磷和酸铝环境的适应机理还不清楚。基于此,本研究以我国南方酸性土壤广泛分布的ECM真菌——粘盖乳牛肝菌Suillus bovinus为研究对象,在纯培养条件下研究了低磷、酸铝胁迫对其生长、营养吸收及菌丝分泌物的影响。结果表明,粘盖乳牛肝菌是一种耐铝型真菌,酸铝胁迫(1 mmol/L)不影响其菌丝生长,而低磷胁迫(20 μmol/L)则显著限制其菌丝生长(P<0.05)。值得注意的是,低磷胁迫的抑制效应可被酸铝胁迫逆转。低磷胁迫显著降低了粘盖乳牛肝菌对磷的吸收(P<0.05),而酸铝胁迫则对菌丝钾的吸收有促进作用。低磷、酸铝胁迫同样改变了菌丝分泌物组成。在低磷胁迫下,大量酚酸类、有机酸及脂质代谢物的积累量下调;而酸铝胁迫下则有大量酚酸类物质上调,有机酸和脂质中上调代谢物数量也高于下调数量;低磷酸铝复合胁迫下酚酸和有机酸类代谢物积累量均显著上调。另外,吲哚-3-乙酸(IAA)在各胁迫下均显著上调。以上结果可在一定程度上解释粘盖乳牛菌对低磷、酸铝环境的适应机理,并对后续进一步阐明ECM的共生适应机理有一定指导意义。     

Exploration of the ability of Coleus blumei to accumulate aluminum

In this study, the capacity of an ornamental species (Coleus blumei) to extract and accumulate aluminum was evaluated. The analyzed parameters were amount of soluble aluminum, radical growth, tolerance rate, bioaccumulation factor, and tissues aluminum concentration. The main limiting factor for aluminum accumulation is the availability of the metal. However, Coleus blumei can grow and accumulate up to 1445.7 mg kg(-1) of aluminum dry base. This plant can play an important role in the treatment of polluted water with metals, since it can grow in conditions with a pH of around 4.8. The aluminum tolerance rate showed for this plant ranged between 18.8% and 25%. Therefore, this species behaves as a non-accumulator, even though the bioaccumulation factor was 3098.5 L kg(-1).     

Aluminum concentrations in tissues of rats: effect of soft drink packaging

Aluminum is a commonly occurring trace element for which no nutritional requirements have been set. Some non-conclusive evidence exists suggesting a need of aluminum for growth, reproduction or health of man and animals. There is concern that exposure or consumption of aluminum may be toxic to humans and animals. The objective of the current study was to compare tissue levels of aluminum of rats fed soft drinks packaged in aluminum cans, glass bottles or distilled water. Thirty male weanling rats (Sprague-Dawley) were divided into three treatment groups of 10 rats each. All rats were fed rodent chow ad libitum throughout the study. Three different fluids, i.e. distilled water, diet soft drinks from aluminum cans and diet soft drinks from glass bottles, were fed for a period of 3 weeks. Aluminum contents of tissues were measured by atomic absorption spectrophotometry. Canned soft drink fed rats had significantly higher blood, liver and bone aluminum concentration than rats that were given glass bottled soft drink. There was a 69% higher bone aluminum concentration and 16% lower femur weight in rats fed aluminum canned soft drinks when compared with rats fed with distilled water.     

铝对植物毒害及植物抗铝作用机理

综述了有关铝对植物的毒害及植物耐铝机理的研究成果。铝可以从植物的不同生物水平上影响植物的生长;不同植物耐受铝的能力不同,耐受性植物可在机体内形成各种耐受机制,以抵抗环境中铝的压力。这在受损土壤环境中的生态系统恢复具有应用前景。     

苜蓿幼苗对铝胁迫的生理响应及综合评价

为探讨铝胁迫对苜蓿(Medicago sativa)幼苗生长和生理特性的影响,对铝胁迫下苜蓿地上和地下生物量、光合色素及根尖胼胝质含量进行测定,并对根尖结构进行观察,最后采用隶属函数分析法对苜蓿耐铝性进行评价。结果表明,随着铝胁迫的增加,苜蓿地上、地下部分生物量呈降低趋势,低浓度和高浓度铝胁迫使苜蓿生物量显著下降(P0.05);苜蓿的叶绿素含量呈下降趋势,胼胝质积累量增多;中、高浓度铝胁迫使根尖胼胝质含量显著上升。随铝胁迫浓度升高,根尖横切面细胞发生较大变化,尤其在高浓度时,细胞干瘪且排列紊乱。隶属函数分析结果表明,No. 12和No. 18苜蓿材料的耐铝性较好,可在南方酸性富铝化土壤中推广应用。     

Zinc status does not affect aluminum deposition in tissues of rats

To examine whether zinc deficiency would increase the toxicity of dietary aluminum, weanling, male Sprague-Dawley rats were fed purified diets containing either 2 or 30 mg Zn/kg diet, with or without 500 mg Al/kg diet for 28 d. Individually pair-fed rats were fed the 30 mg Zn/kg diet with or without added aluminum to control for inanition secondary to zinc deficiency. Rats fed the 2 μg Zn/kg diet showed evidence of zinc deficiency, including anorexia, growth retardation, and depressed concentrations of zinc in tibias and livers. Zinc deficiency did not significantly increase the concentrations of aluminum in the tibias, livers, kidneys, or regions of the brain examined (cerebrum, cerebellum, midbrain, and hippocampus). Inclusion of aluminum in the diet did not alter aluminum concentrations in the various tissues. Under the conditions of this study, zinc deficiency did not result in greater sensitivity to dietary aluminum exposure.     

Aluminum tolerance measured by root growth and mucilage protection in Urochloa brizantha and Urochloa decumbens

Aluminum toxicity on root systems was analyzed through comparing root growth and evaluating the protective function of mucilage in Urochloa decumbens and Urochloa brizantha. Seedlings were grown in a solution with different concentrations of AlCl₃ and with mucilage removed or present. The root elongation rate, total length, number of roots and presence of aluminum at the root apex were measured. Root development was inhibited by aluminum and the elongation rate was maintained without any difference between the two species. A significant reduction in root length was found in U. brizantha. Aluminum did not influence root branching in either species and accumulated mostly in the rhizosphere of U. brizantha, where the mucilage has less of a protective function. The greatest aluminum tolerance was found in U. decumbens, observed through maintenance of total root system growth from lower to higher aluminum toxicity.     

植物适应酸铝胁迫机理的研究进展

酸铝胁迫是限制植物正常生长发育的重要非生物胁迫因子,严重制约了我国酸性土壤地区的农业生产水平。植物抵御酸铝胁迫的形式复杂多样,如分泌有机酸、提高根际pH、分泌黏液、细胞壁对Al³⁺的固定、有机酸对细胞溶质中Al³⁺的螯合与液泡区隔化等。现有研究多集中于常规生理特征分析,缺乏深入的分子生物学解析。基于此,本文对国内外植物适应酸铝胁迫机理的相关研究进行了归纳和总结,从酸铝胁迫对植物生长与生理代谢的影响、植物适应酸铝胁迫最主要的两种生理机制(Al排除机制、Al耐受机制)以及分子水平上调控相关耐铝基因进行了综述。最后针对现有研究的不足提出了展望,以期为深入揭示植物适应酸铝胁迫的机理以及挖掘适于酸土生长的优质作物资源提供理论依据。     

Aluminum tolerance in Pseudomonas fluorescens ATCC 13525: Involvement of a gelatinous lipid-rich residue

Abstract Pseudomonas fluorescens was found to grow in a mineral medium supplemented with up to 50 mM aluminum, complexed to citrate, the sole source of carbon. At stationary phase while virtually no diminution in cellular yield was observed in the presence of 1.0 mM aluminum, only 31% of bacterial yield was recorded in media with 50 mM aluminum. The decrease in soluble aluminum in the culture fluid was concomitant with the formation of a gelatinous residue. At later stages of growth, the trivalent metal was immobilized in this deposit. This bioprecipitate consisted of lipid moieties but was apparently devoid of proteins and carbohydrates. X-ray fluorescence spectroscopy and colorimetric assays also revealed the presence of aluminum and phosphorus. X-ray diffraction spectroscopy indicated that the biomineral was amorphous. Examination of the gelatinous residue by scanning electron microscopy and energy dispersive X-ray microanalysis aided in the identification of aluminum, oxygen and phosphorus rich irregular bodies that were associated with carbon containing thread-like structures.     

Molecular physiology of aluminum toxicity and tolerance in plants

Aluminum being the third most abundant metal in the earth’s crust poses a serious threat to crop productivity in acid soils, which comprise almost half of the arable land. This review travels across time and updates research done on aluminum stress in plants. In its phytotoxic forms, aluminum affects root growth by acting in the root apical zone, resulting in growth inhibition in a very short time at micromolar concentrations. The mechanisms of aluminum toxicity in plants may proceed by growth inhibition, callose accumulation, cytoskeletal distortion, disturbance of plasma membrane surface charge, and H⁺-ATPase activity, lipid peroxidation of membranes, production of reactive oxygen species in cytosol and mitochondria, respiratory dysfunction, opening of mitochondrial permeability transition pores, collapsing of inner mitochondrial membrane potential, activation of mitochondrial protease, and induction of nuclear apoptosis, resulting ultimately in programmed cell death. In contrast, the mechanism of tolerance involves the exudation of organic acid anions, complexation of aluminum with organic acids, and subsequent detoxification. Many oxidative stress genes and other metabolically important genes have also been found to be induced under aluminum stress and overexpression analyses have also shown some plants to develop some degree of tolerance. In the future, researchers in the area of aluminum research should investigate more basic mechanisms of aluminum toxicity and discover and study more aluminum-responsive genes that confer resistance against this toxic metal, to ensure food security for ever-increasing human populations in the future.     

Molecular mapping of genes conferring aluminum tolerance in rice (Oryza sativa L.)

Crop productivity on acid soil is restricted by multiple abiotic stress factors. Aluminum (Al) tolerance seems to be a key to productivity on soil with a pH below 5.0, but other factors such as Mn toxicity and the deficiency of P, Ca and Mg also play a role. The development of Al-tolerant genotypes of rice is an urgent necessity for improving crop productivity in developing countries. Inhibition of root growth is a primary and early symptom of Al toxicity. The present study was conducted to identify genetic factors controlling the aluminum tolerance of rice. Several parameters related to Al tolerance, most importantly the relative root growth under Al stress versus non-stress conditions, were scored in 188 F₃ selfed families from a cross between an Al-tolerant Vietnamese local variety, Chiembau, and an Al-susceptible improved variety, Omon269–65. The two varieties are both Oryza sativa ssp. indica, but showed a relatively high level of DNA polymorphism, permitting the assembly of an RFLP map consisting of 164 loci spanning 1,715.8 cM, and covering most of the rice genome. A total of nine different genomic regions on eight chromosomes have been implicated in the genetic control of root and shoot growth under aluminum stress. By far the greatest effects on aluminum tolerance were associated with the region near WG110 on chromosome 1. This region does not seem to correspond to most of the genes that have been mapped for aluminum tolerance in other species, nor do they correspond closely to one another. Most results, both from physiological studies and from molecular mapping studies, tend to suggest that aluminum tolerance is a complex multi-genic trait. The identification of DNA markers (such as WG110) that are diagnostic for aluminum tolerance in particular gene pools provides an important starting point for transferring and pyramiding genes that may contribute to the sustainable improvement of crop productivity in aluminum-rich soils. The isolation of genes responsible for aluminum tolerance is likely to be necessary to gain a comprehensive understanding of this complex trait. Received: 29 March 2000 / Accepted: 16 August 2000     

Root Growth Inhibition in Boron-Deficient or Aluminum-Stressed Squash May Be a Result of Impaired Ascorbate Metabolism

Although cessation of growth is the most apparent symptom of boron deficiency, the biochemical function of boron in growth processes is not well understood. We propose that the action of boron in root meristems is associated with ascorbate metabolism. Total inhibition of root growth in squash (Cucurbita pepo L.) plants transferred to boron-free medium coincided with a major decrease (up to 98%) in the ascorbate concentration of root apices. Under low-boron conditions, in which root growth was partially inhibited, ascorbate concentration declined in proportion to growth rate. The decline in ascorbate concentration in boron-deficient root tips was not related to ascorbate oxidation. Ascorbate added to the medium improved root growth in plants supplied with insufficient boron. Increasing concentrations of aluminum in the nutrient medium caused progressive inhibition of root growth and a parallel reduction in ascorbate concentration of root apices. Elevated boron levels improved root growth under toxic aluminum conditions and produced root apices with higher ascorbate concentrations. To our knowledge, this is the first report of a correlation between boron nutrition, ascorbate concentration in root apices, and growth. These findings show that root growth inhibition resulting from either boron deficiency or aluminum toxicity may be a consequence of disrupted ascorbate metabolism.     

铝毒胁迫对乐昌含笑幼苗生长和生理的影响

为研究铝毒对乐昌含笑Michelia chapensis幼苗生长的影响,采用水培法对乐昌含笑幼苗进行铝胁迫实验,设置铝浓度梯度为0 (CK)、0.5 (T1)、1 (T2)、2 mmol·L^-1(T3)共4个处理,定期测定其根长、根尖铝含量、POD和CAT活性、MDA和脯氨酸(Pro)含量。结果表明,铝胁迫明显抑制乐昌含笑根的伸长生长,随着Al³⁺浓度的增加,抑制程度加剧,T1、T2、T3与CK对照比较,相对伸长率分别为84.53%、63.16%和54.46%;根尖铝含量随处理时间延长和铝浓度增加而增加,处理6 d时T1、T2、T3根尖铝含量分别是CK的 63.64、82.60、121.69倍;POD、CAT酶活性与处理时间和铝浓度呈正相关,各处理6 d时POD活性比处理1 d提高17.00%～115.21%,CAT活性提高25.11%～49.28%;MDA和Pro含量变化随着胁迫时间和铝溶液浓度的增加而增加,处理6 d 时T1、T2、T3的MDA含量比CK对照增加46.13%～59.78%,Pro含量增加60.12%～150.85%。在铝胁迫条件下,乐昌含笑根尖铝含量增加,根的伸长生长受抑制,细胞膜膜质过氧化程度增加;乐昌含笑可通过激活体内抗氧化酶系抵抗铝胁迫,同时产生脯氨酸调节细胞渗透势。